“Good Morning America” star Robin Roberts publicly came out as a lesbian on Facebook on Sunday when she posted a message thanking her girlfriend for supporting her during her battle against cancer.

Roberts’ sexuality has been an open secret in media circles, but the ABC TV personality finally acknowledged it to her legions of fans while reflecting on her health struggles.

“I am grateful for my entire family, my longtime girlfriend, Amber, and friends as we prepare to celebrate a glorious new year together,” Roberts wrote. “I am grateful for the many prayers and well wishes for my recovery. I return every one of them to you 100 fold.”

Roberts was diagnosed with breast cancer in 2007 and then last year had to fight a rare blood and bone-marrow disorder triggered by her treatments.

She eventually received a life-saving transplant from her sister Sally-Ann Roberts, a TV news anchor in New Orleans.

“Flashback 12/29/12….Hard to believe this was 1 year ago today..when I reached a critical milestone of 100 days post transplant,” Roberts noted in her message.

“I am grateful for my sister, Sally-Ann, for being my donor and giving me the gift of life.”

Roberts’ gal pal, Amber Laign, is a San Francisco native who works as a massage therapist in New York, specializing in patients recovering from serious injuries.

The pair has been together for 10 years. They met through mutual friends.

Earlier this month, Roberts made a brief, passing reference to her unnamed girlfriend while speaking to a women’s conference by way of closed-circuit television.

Roberts had been asked about being honored at the ESPY Awards with the Arthur Ashe Award for Courage.

“My brother was there, my sister was there, my girlfriend was there — all the people who mean the most to me were there,” she told attendees of the Massachusetts Conference for Women.

The statement wasn’t reported in any national media.

ABC News spokesman Jeffrey Schneider said in a statement Sunday: “We love Robin and Amber, who we adore and have all known for a long time.

“We were so touched by [Roberts’] Facebook message today and so thankful for all the loving support she has in her life.”

In addition to her health battles, the former ESPN anchor is best known for her historic 2012 interview with President Obama, when he announced his support for same-sex marriage.